1. Field of the Invention
This invention relates to an image displaying apparatus and an image pickup apparatus having the same, and is suitable for displaying an image on a predetermined surface by the use, for example, of scanning means (referred to also as optical scanning means) for two-dimensionally raster-scanning the predetermined surface by a light beam optically modulated on the basis of image information and emitted from light source means, and observing the image on the predetermined surface through an optical system.
2. Related Background Art
In an image displaying apparatus such as an electronic viewfinder system used in a digital camera, a video camera or the like, design is made such that a two-dimensional display element such as transmission type liquid crystal or reflection type liquid crystal and an eyepiece optical system are combined together, and an image formed on the two-dimensional display element is displayed and observed as a virtual image.
In recent years, in such an image displaying apparatus, it has been required for the displayed image to be of higher definition. For such a requirement, in the aforedescribed display element, a number of pixels corresponding to the number of pixels necessary on the display element must be manufactured, and this has led to the problem that the defect of the pixels increases by an amount corresponding to the increase in the number of pixels, or the pixels become small relative to the size of the two-dimensional display element and the manufacture thereof becomes difficult. Further, in a two-dimensional display element utilizing liquid crystal, the response speed of the liquid crystal is low, and this has led to the problem that when a moving image is displayed, there remains an afterimage.
On the other hand, there is known an image displaying apparatus for displaying an image by scanning a surface to be scanned by the use of optical scanning means capable of two-dimensionally scanning a light beam from light source means optically modulated on the basis of image information, instead of the use of a two-dimensional display element, and observing the image (e.g. U.S. Pat. No. 5,467,104). U.S. Pat. No. 5,467,104 shows the technique of scanning red, blue and green light beams in a two-dimensional direction, i.e. horizontal and perpendicular direction, by scanning means, and directly forming a two-dimensional image on a retina through the optical system.
Such an image displaying technique scans a light beam and displays an image, and therefore, need not use a display element formed with a plurality of pixels in accordance with necessary resolution as in the image displaying apparatus using the two-dimensional display element, and has a feature that, in principle, the defect of pixel does not occur.
In realizing such an image displaying apparatus using the scanning means, a micro electro-mechanical system (hereinafter referred to as the MEMS technique) manufactured by a semiconductor process is known as the optical scanning means (e.g. U.S. Pat. No. 5,606,447 (Japanese Patent Application Laid-Open No. H7-175005 and Japanese Patent Application Laid-Open No. H8-334723)).
Optical scanning means manufactured by the MEMS technique is compact and light in weight and capable of operating at a high speed, and such features are suited as an image displaying apparatus. Also, it is known that the MEMS technique of two-dimensional scanning means of head mount type for an image displaying apparatus (e.g. SPIE Conference 4407,19 (June 2001) Wafer Scale Packaging for a MEMS Video Scanner). The optical scanning means by these MEMS techniques is such that a surface reflecting light is mechanically resonance-operated by a torsion bar or the like, and torsion occurring at that time is utilized to incline the surface reflecting light and deflect and scan light incident on the reflecting surface. Since torsion is utilized, the surface reflecting light is not rotated but rocked.
The basic frequency of these mechanical resonance operations is determined by the mechanical dimensions of the optical scanning means. The optical scanning means is driven by the resonance drive by electrostatic power and electromagnetic power.
In the aforementioned U.S. Pat. No. 5,467,104, etc., the optical scanning means of such a resonance type is defined as a first direction and optical scanning means for scanning light in a second direction different from the first direction is disposed to thereby realize two-dimensional scanning.
When an image displaying apparatus using scanning means is applied to an electronic viewfinder system for use in an image pickup apparatus such as a digital camera, it is desired to display a subject, which is a moving object, on the image displaying apparatus on real time and make an observer observe it. Accordingly, for a subject moving at a high speed, an apparatus in which the frame rate of an image is fast becomes necessary.
In the aforementioned U.S. Pat. No. 5,467,104, U.S. Pat. No. 5,606,447 (Japanese Patent Application Laid-Open No. H7-175005) and Japanese Patent Application Laid-Open No. H8-334723, the technique of displaying an image by the use of scanning means is merely disclosed.